Sharif Digital Repository

Core-shell structures of Ag@Pt nanoparticles (NPs) dispersed on Carbon Vulcan XC-72, Multiwalled carbon nanotube and reduced graphene oxide (rGO) support containing different Ag:Pt mass ratios and applied to the oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell (PEMFC) were synthesized by the ultrasonic and reduction treatment method. The morphology of as-prepared catalysts characterized by the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and induced coupled plasma atomic emission spectroscopy (ICP-OES). The ORR activities and stabilities of catalysts were studied through electrochemical measurements utilizing the Cyclic Voltammetry... 

The vivid optical properties of gold nanorods (AuNRs) arising from their unique structural anisotropy have been an object of fascination in a broad range of applications over the past decade. The pseudo-one-dimensional rod-shaped morphology of AuNRs underlies two distinct LSPR bands attributed to the longitudinal and the transversal oscillation of the surface plasmons. Indeed, the brilliant and high-contrast rainbow color tonality of AuNRs primarily emanates from the dramatic dependency of the location of the aforementioned bands on the aspect ratio of the nanorods. It is so profound that a minute increment of the aspect ratio is followed by a significant redshift of the longitudinal peak... 

Nowadays, biocompatible composites are being utilized as scaffolds supporting cell growth promotion and features with the aim of organs regeneration or substitution based on tissue engineering principals. Moreover, in order to improve bioscaffolds features and function, various two-dimensional composite fillers have been under investigation; for instance, Graphene, Boron nitride, Metal dichalcogenides and oxides and black phosphorous and also electrospinning is mentioned as one of the most compatible and conventional processes of scaffold design that is also the main method of fabrication in this study. In addition, it should be pointed that biocompatible polymers and particularly natural... 

The aim of this study is the fabrication of 3D porous PCL scaffolds contain core-shell fibers for cartilage tissue engineering. The novel fabrication method is co-axial wet electrospinning simultaneously. These tablets like scaffolds have superior porosity and pore sizes for cell culturing and cell-cell interaction as they have good mechanical properties for cartilage tissue engineering in comparison to 2D electrospun scaffolds. The structure of these 3D scaffolds is mimicking the ECM of cartilage. This study presents the coaxial electrospinning of PCL nanofibers encapsulated with bovine serum albumin and platelet rich plasma for demonstration of controlled release and bioactivity retention,... 

Synthesis, characterization and photocatalytic applications of core-shell like ZnO@CdS nanorods have been studied in this research. The synthesis of core-shell like ZnO@CdS nanorods was carried out in three different steps. At first, ZnO seed layer was formed on glass substrate via sol-gel process under optimum conditions using absolute ethanol solution containing zinc acetate and a stabilizer ( either Monoethanolamine (MEA) or diethanolamine (DEA)). When MEA used as stabilizer, the optimum concentration of sol was found 0.2 M, while increasing the sol concentration caused the seed layer to be grown in a string-like structure. The RMS surface roughness of seed layer prepared by 0.2 M sol... 

In this report, a combination of in-situ chemical synthesis and electrolysis methods was applied for the preparation of zinc oxide/graphene quasi core-shell nanoparticles. Pure zinc oxide was also prepared using the same method at different temperatures. The degree of 100 ◦C was selected for synthesizing of ZnO-GO quasi core-shell (zinc oxide as a core and few layer of graphene oxide as a shell). The particle size was 15±2 nm in all samples. In both processes, oxygen was the main reason for the connection between the core and the shell. Unlike chemical process that has all kind of functions in electrolysis process, one kind of function was produced and confirmed by FTIR. XRD patterns also... 

Hydrophilic polymers are widely used in enhanced oil recovery (EOR) processes to increase water viscosity during polymer flooding. However, these polymers increase the viscosity of injected water in undesirable strands, before reaching considerable positions that make some problems in polymer flooding process such as thermal, mechanical, bacterial degradation, surface absorption and undesirable plugging. In this study, a novel core-shell structure of polyacrylamide as an active polymer and nanoscale coating polystyrene as a shell polymer was designed and prepared to intelligently control mobility ratio in oil reservoirs and overcome weakness and limitations of classical polymer flooding.... 

Superparamagnetic core/shell nonporous (S1) and core/shell/shell mesoporous (S2 and S3) nanocomposite magnetite/silica particles with a magnetite cluster core of 130±30 nm, a nonporous silica shell of 90±10 nm thickness, and a mesoporous silica shell of 70±15 nm thickness were prepared thorough a simple method. Mesoporous particles were prepared with two BJH pore sizes (2.44 for S2 and 3.76 nm for S3 particles, respectively). The fabricated S1, S2 and S3 particles present high saturation magnetization values of 20, 13 and 17 emu/g, respectively. As a biological application, the lipase from Pseudomonas cepacia was successfully immobilized onto the amino-functionalized nanocomposite particles... 

This thesis deals with a theoretical and experimental investigation of different approaches for reduction of electronic recombination in the semiconductor/Dye interface of dye sensitized solar cells (DSSC) including dye coverage, core-shell structures and energy level distributions. Interface of ZnO/TiO2 in the core-shell structure have been studied by density functional theory and the energy level distribution of surface atoms, recombination and Fermi level changes, open circuit voltage and surface dipole distributions have been discussed.
The presence of TiO2 shell increases the ZnO surface dipole moment, and shifts the ZnO conduction and valence bands to higher energies. Also, it...